A direct-sequence or direct sequence coding spread spectrum communication technique in essence combines two digital signals, or bit streams, to create a third signal prior to transmission. The first signal is an information signal, such as the output of a digitized voice circuit. For example, the first signal may have a bit rate of 10 kb/s. The second signal is generated by a random-sequence, or pseudonoise (PN) generator, and is a stream of essentially random bits having a bit rate that is several orders of magnitude greater than the bit rate of the digitized voice signal. The modulation of these two signals results in the third signal having the same bit rate as the second signal. However, the third signal also contains the digitized voice signal. At the receiver, an identical random-sequence generator produces a random bit stream which mirrors the original random-sequence that was used for modulation at the transmitter. For proper operation, after carrier frequency de-modulation, the PN generator of the receiver must be synchronized to the incoming PN sequence. By removing the random sequence from the received signal and integrating it over a symbol period, a despread signal is obtained. Ideally, the despread signal exactly represents the original 10 kb/s voice signal.
The TIA/EIA Interim Standard, Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System, TIA/EIA/IS-95 (Jul. 1993) specifies in Section 6.1.2 that a mobile station must provide two independent techniques for output power adjustment. These two techniques are an open loop estimation, based solely on mobile station operation, and a closed loop correction that involves both the mobile station and the cell site controller, or base station. In the latter technique the mobile station responds to power control bits received over a Forward Traffic Channel and adjusts its mean output power level in accordance with these bits. In the former technique a measurement of received signal strength from the base station is used to control the output power.
The power control in the CDMA system is also described at pages 10 and 12, and shown generally in FIG. 3-2, in a publication entitled "Introduction to CDMA and the Proposed Common Air Interface Specification (CAI) for a Spread Spectrum Digital Cellular Standard-An Overview of the Application of Code Division Multiple Access (CDMA) to Digital Cellular Systems and Personal Cellular Networks", QUALCOMM Incorporated, Mar. 28, 1992. As is described in this publication, the goal of the mobile station transmitter power control process is to produce, at a cell site receiver, a nominal received signal power from each mobile station transmitter that is operating within the cell. If all mobile stations are so controlled, the end result is that the total signal power received at the cell site from all of the mobile stations is equal to the nominal received power, times the number of mobile stations.
The following U.S. Patents and other publications pertain to the teaching of this invention. U.S. Pat. No. 5,168,505 to Akazawa et al., issued Dec. 1, 1992 and entitled "AUTOMATIC GAIN CONTROL DEVICE FOR SPREAD SPECTRUM COMMUNICATION DEVICE".
U.S. Pat. No. 5,107,225 to Wheatley, III et al., issued Apr. 21, 1992 and entitled "HIGH DYNAMIC RANGE CLOSED LOOP AUTOMATIC GAIN CONTROL CIRCUIT".
U.S. Pat. No. 5,099,204 to Wheatley, III, issued Mar. 24, 1992 and entitled "LINEAR GAIN CONTROL AMPLIFIER".
U.S. Pat. No. 5,093,840 to Schilling, issued Mar. 3, 1992 and entitled "ADAPTIVE POWER CONTROL FOR A SPREAD SPECTRUM TRANSMITTER".
U.S. Pat. No. 5,132,985 to Hashimoto et al., issued Jul. 21, 1992 and entitled "SPREAD SPECTRUM RECEIVER".
U.S. Pat. No. 5,056,109 to Gilhousen et al., issued Oct. 8, 1991 and entitled "METHOD AND APPARATUS FOR CONTROLLING TRANSMISSION POWER IN A CDMA CELLULAR MOBILE TELEPHONE SYSTEM".
U.S. Pat. No. 4,993,044 to Akazawa, issued Feb. 12, 1991 and entitled "SPREAD-SPECTRUM COMMUNICATION RECEIVER".
U.S. Pat. No. 4,901,307 to Gilhousen et al., issued Feb. 13, 1990 and entitled "SPREAD SPECTRUM MULTIPLE ACCESS COMMUNICATION SYSTEM USING SATELLITE OR TERRESTRIAL REPEATERS".
PCT International Application No. WO 93/10609, published 27 May 1993 and entitled "ADAPTIVE POWER CONTROL FOR A SPREAD SPECTRUM COMMUNICATIONS SYSTEM AND METHOD".
PCT International Application No. WO 93/07702, published 15 Apr. 1993 and entitled "TRANSMITTER POWER CONTROL SYSTEM".
PCT International Application No. WO 93/05585, published 18 Mar. 1993 and entitled "A METHOD FOR AUTOMATIC TRANSMISSION POWER CONTROL IN A TRANSCEIVER SUITABLE FOR A CDMA ENVIRONMENT EMPLOYING DIRECT SEQUENCE DIFFUSION".
PCT International Application No. WO 92/21196, published 26 Nov. 1992 and entitled "METHOD AND APPARATUS FOR CONTROLLING TRANSMISSION POWER IN A CDMA CELLULAR MOBILE TELEPHONE SYSTEM".